电力变压流偏磁问题的研究.docVIP

河 北 工 业 大 学 毕业设计说明书 作 者： 耿铮 学 号： 110644 学 院： 电气工程学院 系(专业)： 电气工程及其自动化 题 目： 电力变压器直流偏磁问题的研究 指导者： 刘宏勋 副教授 评阅者： 李永建 副教授 2015 年 6 月 日 毕业设计（论文）中文摘要 电力变压器直流偏磁问题的研究 摘要： 直流电流通过交流电网中中性点接地变压器的绕组，会导致变压器处于异常工作状态，严重影响供电质量和继电保护系统的工作。对电力变压器直流偏磁问题的研究意义重大。 首先，本文简介了课题的研究现状，阐述了在交流电网中产生直流电流的原因，并分析了单相变压器直流偏磁的机理。 进而，利用SIMULINK平台将单相变压器在过励磁与直流偏磁状态下的励磁电流波形以及谐波含量进行对比,观察铁心磁滞回线变化趋势，并搭建三相三柱变压器模型与三相变压器组模型，比较二者承受直流偏磁的能力。 结果表明，直流偏磁时，变压器励磁电流半波饱和，峰值增大且二次谐波含量明显升高；铁芯磁滞回线向右上偏移；三相三柱变压器比三相变压器组有更好的直流偏磁承受能力。 关键词： 电力变压器 直流偏磁 励磁电流 谐波 MATLAB/SIMULINK 毕业设计（论文）外文摘要 Title The Study of Issue about Power Transformer under DC Bias Abstract DC flowing into transformer windings through neutral points is an abnormal work situation of the transformer. It affects power supply quality and the correct operation of the relaying protection system. Therefore, the study of the study on DC bias of a power transformer is of great importance. Firstly, the present status of research on this issue is generally introduced. And the reason of appearance of DC in the AC grid is elaborated. Next, the mechanism of DC bias in a single phase transformer is analyzed. Secondly, a simulation model of single phase transformer is established utilizing MATLAB/SIMULINK. Under over excitation and DC bias situation, the waveform and harmonics values of exciting current are compared. Meanwhile, the variation trend of iron core hysteresis curve is obtained. Also, the model of three-phase three-leg transformer and three-phase main transformer are established to compare their ability to bear DC bias. The results of simulation show that when DC bias in a transformer happens, the iron core of the transformer will be saturated semi-periodically. The peak value and secondary harmonic component in the exciting current will increase significantly. Meanwhile, iron hysteresis curve will move